Sheet and plate stretching apparatus



Feb. 14, 1961 M. D. STONE HAL 2,971,557

SHEET AND PLATE: STRETCHING APPARATUS Filed Sept. 23 1957 5 Sheets-Sheet1 .h ,.N @E I Wn INVENTORS MORRIS D. STONE' Ho WAR 171.3 A TTORNEY Feb.14, 1961 M. D. STONE ErAL SHEET AND PLATE STRETCHING APPARATUS FiledSept. 25. 1957 3 sheets-sheet 2 s T n mw n. N m n M man. W M7 A u @WH .Yam muznow MN umamwuf. .525m nzxw u 3 UGM )Gm No8 m no3 53 vu mm mu 5% vmFeb. 14, 1961 M, D, STONE ErAL 2,971,557

SHEET AND PLATE STRETCHING APPARATUS Filed Sept. 23, 1957 5 Sheets-Sheet5 INVENTORS /t/oQ/s D. S70/VE 755/@ ,4free/ver United States Patent O 'iSHEET AND PLATE STRETCHING APPARATUS Morris D. Stone and Howard H.Talbot, Pittsburgh, Pa.,

assignors to United Engineering and Foundry Company, Pittsburgh, Pa., acorporation of Pennsylvania Filed Sept. 23, 1957, Ser. No. 685,490

2 Claims. (Cl. 153-35) This invention relates to apparatus forprocessing elongated metal workpieces such as sheets and plates and inparticular relates to apparatus for stretching aluminum alloy sheets andplates by securing them at their ends between two elements and thenmoving the elements relative to one another to cause the plates to beelongated to the extent desired, a safety feature being included in theapparatus for protecting the apparatus and the foundation upon which itis mounted.

There are many types of sheet and plate stretching apparatus presentlyin use for processing relatively light gauge strip, where the totalforces required to accomplish the particular stretching operation isrelatively low, so that in the event a workpiece breaks while theoperation is in progress, the shock imposed upon the elements making upthe apparatus as well as upon the foundation to which the apparatusframework is secured is not too serious. However, for stretchingrelatively heavy gauge sheets and plates, unless precautions are takenfor absorbing the shocks incident to the failure of certain op eratingelements or to the breakage of the workpieces themselves while beingstretched, serious damage to the apparatus as well as to the foundationupon which the apparatus is mounted will result. Moreover, in eX-tremely large capacity stretching apparatus as presently employed, evenunder normal operating conditions eX tremely large and objectionableforces are imposed upon the foundation.

1t is an object of this invention to provide in a plate and sheetstretching apparatus means for absorbing the shock, due to the energysuddenly released, upon the apparatus such as that incident to thebreakage of a workpiece while undergoing a stretching operation.

It is another object of this invention to provide in a workpiecestretching apparatus a base so constructed and arranged with respect tothe remaining portion of the apparatus as to permit shocks to beabsorbed in motion rather than by being transmitted from the apparatusdirectly to a foundation rigidly connected thereto.

1t is still another object of this invention to provide a plate andsheet stretching apparatus for stretching relatively heavy sheets andplates which is rugged of construction and capable of absorbingeffectively any shocks which may be imposed thereon without causing anydamage to be suffered by the elements or the supporting foundation.

A further object of this invention is to provide a plate and sheetstretching apparatus which is economical to construct as well asrelatively inexpensive to maintain under service conditions.

These objects as well as the various other novel features of thisinvention will become apparent from the description and accompanyingdrawings of which:

Fig. 1 is a sectional elevation of a stretching apparatus embodying thefeatures of this invention;

Fig. 2 is a partial sectional View taken at II-II of Fig.

2,971,557 Patented Feb. 14, 1961 Fig. 3 is a front' elevation view takenat III-III of Fig.

Fig. 4 is an enlarged end elevation view taken from the right of Fig. 1;

Fig. 5 is a schematic diagram of the hydraulic control system for theworkpiece gripping elements of the stretching apparatus;

Fig. 6 is a partial side elevation taken at the right of the apparatusshown in Fig. l but embodying a modification of the invention hereindisclosed;

Fig. 7 is a plan view of the apparatus shown in Fig. 1; and

Fig. 8 is an enlarged side elevation view of the pinch rolls associatedwith one of the jaw heads.

With reference to the drawings, the workpiece stretching apparatusconsists of a normally stationary gripper head 11, a movable workpiecegripper head 12, two compression bars 13 having openings 14 thereinalong their length into which there are extended suitable pins 11asecured to the normally stationary workpiece gripper head 11 forsecuring the head at a desired location along the bars 13, and apiston-cylinder assembly 15 of which piston 16 is secured at its outerend to a crosshead 17 which in turn is connected by two links 1S to themovable gripper head 12. The piston-cylinder assembly 15 is securedwithin an entablature 19 having secured to its under portion a platform21 which is slidably mounted upon a base 22. To the two sides of theentablature, one end of each of the bars 13 is rigidly secured therebyconnecting the entablature to the stationary gripper head. in thisarrangement under stretching operation the entablature, bars andstationery gripper head are mechanically connected together as a unit.Attached to the front end of the base 22 there are two relatively smallpistoncylinder assemblies 23, the pistons 24 ot which are constantlyurged in contact with the front portion of the platform 21 therebymaintaining the entablature 19 and piston-cylinder assembly 15 in theirmost extreme left hand position as shown in Fig. 1 so that the oppositeends of the platform 21 abut against suitable stops 25 which are alsosecured to the base 22. It is to be appreciated that the capacity of thepiston-cylinder assemblies 23 is such that under normal operation of thestretcher, the assemblies 23 will prevent any longitudinal movement ofthe entablature in the direction toward the cylinders. However, theassemblies 23 are so designed as to permit the entablature to move aslight amount when abnormal horizontal forces are encountered such asthose caused when sudden breakage of a workpiece occurs and are ofsu'cient capacity to return .the assembly to its original position.Although piston-cylinder assemblies 23 have been shown for purposes ofillustration, any type of yieldable means may be employed for thepurpose such as springs, for example.

Extending through the entablature 19 and at op-positely disposed pointswith respect to one another, there are two pull back piston-cylinderassemblies 26 of which the pistons 27 are secured at their ends to thecrosshead 17, the crosshead being slidably mounted upon a suitable.platform 23.

With particular reference to Fig. 3, it is noted that the entablature 19is rigidly secured to the ends of the compression bars 13 whereas thelinks 18 are attached to the movable gripper head 12 and pass alongsuitable guiding surfaces 29 in the side of entablature 19, and extendto a point adjacent to the crosshead 17 to which they are secured bysuitable pins 31. In order to prevent the entablature 19 from beingdisplaced sideways with respect to the base 22, suitable side plates 32are welded to the base 22 at spaced points on either side thereof.Similar plates 3v 33 are secured to the platform 28 for preventingsideways displacement of the crosshe'ad 17. Y

For securing a plate atV its ends between the gripper heads, each headvis'provided with a tapered opening 34 within which a plurality of pairsof suitable gripper jaws 35 are slidable received, being mov-able intoand out of their gripping positions by push rods 36 and 35a secured attheir outer ends to levers 37 and 35 respectively acuatable by aplurality of piston-cylinder assemblies connected thereto and to the topof each head.

4Between the two gripper heads there are shown two longitudinal supportcarriages 4,1 which are spaced apart from one another and vsupported bythe compression bars 13 and serve to support the workpiece along itslength. Each of these carriages isV provided with rollers 41h andytransversely movable side guards 4117 which, through the individualframe work supporting each one, are` connected to a right and left 'handthreaded screw 41e. The guards 41b are arranged t'o be movedtransversely relative to the longitudinal center of the stretcher onrotation of the screw 41C, by means of a hand wrench or the like, inorder to center the workpiece prior to the gripping and subsequentstretching operations.

It is a feature of the gripper heads that the push rods 3,6 thereof arerelatively thin compared to their lengths, thereby being rather limber,so that when compressive Yforces are imposed thereon in a longitudinaldirection on breakage of a workpiece during a stretching operation, therods will immediately elastically buckle and consequently draw open thejaws and release the ends of the workpiece held therebetween. Then, too,in order to prevent exceptionally high pressures from being built upinstantane- A,ously in the piston-cylinder assemblies 39' should ayworkpiece break during a stretching operation, the pistoncylinderassemblies 39 'are opened to exhaust soon after a stretching operationbegins so that there will be no pushing action imposed upon the rods inopposition to the forces which will be encountered bythe rods whenbreakage of a workpiece occurs. By this'construction, the jaws, theircylinders and the elements associated therewith are automaticallyrelieved o f the full impact forces incident to the breakage of aworkpiece. lFurthermore, the end of the plate is quickly released and ispermitted to pass through the jaws and strike'against the gripper headitself so that a considerablepart of the impact energy of the brokenplate is absorbed by the head rather than by the jaw assembly itself-`Spaced along the length of the two bars lnthererare several pairs offrames 42, the details of which are shown in Fig. 4, which are providedwith shoulders 43 for engaging with and supporting the bars 13` atspaced points along their lengths. The bars 13 are rigidly connectedtothe frames 42 by means of suitable bolts which pass through openingsin the frames and the bars, each of frames 42 being slidably supportedupon a base 44. So that the frames 42 will be prevented from beingdisplaced transversely with respect to the base 44, there are providedfor each assembly a central guide key 45 between the frame 42 and thebase 44 and a pair of C clamps 46 whiich are secured to the frames 42 bymeans of suitable stu s.

Also as shown in Fig. 4, there is attached to the adjustable gripperhead 11 a frame 47 extending downwardly therefrom and upon which thereare rotatably mounted reels 48, 49 andV 51 which serve to retrieve andpay out the electrical wires connected topa power source and to the headadjusting motor 52 and other electrical equipment associated with theheads. The motor 52 as well as the adjustable gripper head 1l and itsrelated parts are mountedpuponra carriage'SS, the wheels 4 of which ridealong the upper surface'of the bars 13. Stops S Yareprovided at theends'of suitable track extensions '552; which are secured to the ends ofbars 13 and sup-A ported from beneath "by struts SSb: `A cross "brace'55C is connected to the track extensions at their outer ends.

einen 4 The motor 52 is connected in driving relationship to a worm geardrive 56 which, in turn, through shafts 57, is connected to a pair ofbevel gear drives 58, the output shafts S9 of which extend verticallydownward therefrom and upon the lower ends of each shaft there ismounted a pinion 61 which engages with a rack 62 secured to each bar 13at its inner, face.

'lust forward of each'of thel gripper heads 11 andv 12 there is a pairYof pinch rols 63`and 6.3, the lower one 63 being driven bymeansof asuitableA motor, not shown', and adjustable vertically by means of ajack screw 64 threadably attached to the carriage53. The upper pinchroll 63a is mounted upon Van arm 65 which is pivotally supported uponYthe carriage 53A and movable into and out of engagement with the lowerroll by means of suitable piston-cylinder assemblies, not shown,connected to the arm 65 and to the carriage S3. Thus, by means of thevertically adjustable lower pinch rolls, it is possible to compensatefor dierent plate thicknesses 'so as to maintain the workpiece attheproper level and in align ment with the gripper heads.

ln Fig. 5 there is shown a schematic diagram of the hydraulic controlsystem employed in conjunction with the piston cylinder assemblies 39,push rods 36 and 36a and jaws 35, which they actuate, of the stationarygripper head 11, the same control arrangement being employed for thevarious elements of the gripper head 1?.. In this particulararrangement, five sets or pairs of assemblies are employed, beginningwith a central pair 39C1 and continuing in an outward transversedirection through pairs 39C2, 39C3, 39.; and 39C5. As noted in Fig. 5,each assembly of each pair is disposed an equal distance on either sideof the center line of the apparatus.'Y For controlling the movement ofeach pair of gripper push rods 36 and 36a, a system of controls isprovided for causing the` separate pairs ofprods, and consequently thejaws actuated thereby, to beoperated in sequence so that the centralpairs Vof. jaws will first grip "the workpiece and Vthen at Vintervalsdetermined by the build up of pressure in piston-cylinder assembly 3 C1,working pressure. Vis introduced into the next adjacent piston-cylinder39C2 to cause the jaws controlled thereby to vclose until finally all ofthe gripper jaws will be'clamped across one end of the workpiece. Thissame action will also take place at the gripper head 1,2.

Since the control for each pair of assemblies is practically the same,and, further, since the actuation of each pair of succeeding assembliesdepends upon actuation of the pair preceding, it is considered to besufficient to describe only the controls for the irst two pairsofassemblies 39C1 and 39C2 and the push rods and jaws operated thereby. Tothe assemblies 39C1 there are connected two hydraulic lines which mergeinto one and to which there is connected a balance piston type reliefvalve 39V1 which communicates with the main pressure line PLp a rightangle type check valve 39CV1, which also is connected to the mainpressure line, and a balance piston type relief valve 39V2, which valveis, in turn, connected to the second pair of piston-cylinder assemblies39C2, as shown in Fig. 5. The next succeeding pairs of piston-cylinderassemblies 39C3, 39C.,E and 39C5 are connected together to the mainpressure source in a fashion similar to that in which piston cylinderassemblies 39C1 and 39C2 are interconnected, valves 39V3 and39V4 beingconnected rto assemblies 39C3 and 39C4 respectively. VSince vtheassemblies 39C5 are the last in the group, it is not necessary toprovide a separatek piston type relief valve therefor. From the oppositeend of each of the piston-cylinder assemblies, separate lines extend andthey are directly connected to a second hy draulic line 'PL2 whichcommunicates with a reversing valve and to which line PL1 is v.alsoconnected through balanced .piston type relief valves BRV1 and BRVZ, thepurpose of the reversing valve being to introduce uid under pressure toeither end of the piston-cylinder assemsemblies 39C1, thereby to causethe push rods 36 and `36a to close the jaws 35 to grip the end of theworkpiece. As soon as gripping of the workpiece by the first set of jawstakes place, due to the build up of pressure 1n the rst piston-cylinderassembly 39C1, the valve 39V1 i opens at the top thereby permitting uidunder pressure to pass to the second valve 39V2 and consequentlytherethrough and to the pair of piston-cylinder assemblies '93C2. Assoon as the jaws actuated by piston-cylinder .assemblies 39C2 grip theworkpiece, the next succeeding assemblies 39C3 are actuated on suicientbuild-up 'of pressure within the assemblies 39C2 to cause uid to flowfrom the upper portion of the valve 39V2 to the valve 39V3 andconsequently to the piston cylinder aszsemblies 39C3. This sequence ofoperation continues `until all of the jaws 35 are clamped upon theworkpiece. Y-By this arrangement, ironing out or attening of the`workpiece at the ends `is quite readily accomplished. For 'releasingthe workpiece from the jaws, it is merely neces- :sary to reverse valveRV to cause lluid to liow into line VPL2 to the opposite ends of thepiston cylinder assemblies thereby to actuate all of the push rods atIthe same time and to open the jaws.

At times, it may be desirable to close all of the workpiece grippingjaws 35 simultaneously rather than in sequence. This is accomplished bylocking together all of the links 37 by passing a key 40a, as shown inFig. 6, through suitable transversely in line openings 40 provided ineach of the links 37. The valves 39V1, 39V2, 39V3, 39V4 and 39V5 are, ofcourse, adjusted so as to permit the high pressure fluid from line PLIto llow directly and simultaneously to all of the piston-cylinderassemblies 3901, 39C2, 39GB, 39C., and 39C5. Should ere be anyirregularities such as high spots along the width of the workpiece, thenthe jaws adjacent thereto will first make contact with the workpiece andconsequently the pressure coming to bear upon the workpiece at thatinstant will be the total pressure of all of the piston-cylinderassemblies so that flattening of the workpiece at that point will bereadily accomplished. Flattening of the workpiece will continue acrossits width and iinally all of the jaws will be in gripping relationshiptherewith. A

In Fig. 6 there is shown a modification of the invention hereindisclosed in which therev are provided pistoncylinder assemblies 66,secured to the foundation, which .engage with the ends of the bars 13and serve the same purpose as the piston-cylinder assemblies 23 as shownand described in the preferred form of invention. As .in the case of thepiston-cylinder assemblies 23, the as- -semblies 66 serve to opposemovement of the entablature- ;side bar-stationary gripperhead-combination to the right ,at the time a stretching operation isbeing carried out vand yet will yield suflciently to permit thisassembly to move to the right in the event breakage of a workpieceoccurs during a stretching operation, thereby preventing damage to theapparatus. As in the case of the piston-cylinder assemblies 23, thepiston-cylinder assem- In operation, the apparatus embodying thefeatures of the invention in preferred form as herein disclosed may 1 bebriey summarized as follows:

Depending upon the initial length of workpiece upon 1 which a stretchingoperation is to be performed, the

normally stationary gripper head 11 is moved along the compression bars13 to the desired position depending upon the length of workpiece to bestretched and then secured in place by extending the pins 11a, which areconnected to the head 11, through the adjacent openings 14 in the bars13. Depending upon the thickness of the workpiece to be processed, thelower pinch rolls 63 are either raised or lowered in order that thecenterline of the workpiece supported thereby will be in alignment withthe jaws. By means of a crane or the like, a workpiece is deposited uponthe pinch rolls 63 and the support carriages 41, and pinch rolls 63rotated to feed one end of the workpiece into the jaws of the gripperhead 11 and then the movable head 12 moved into position for grippingthe opposite end of the workpiece. Pressure is applied to thepiston-cylinder assemblies 39C1, 39C2, 39C3, 39C4 and 39C5 either insequence or simultaneously and the workpiece ends gripped by jaws 35.Pressure is then introduced into the piston-cylinder assembly 15 causingthe crosshead 17 to move to the left, as viewed in Fig. 1, thereby topull the gripper head 12 in the same direction causing the .workpiece tobe stretched. As soon as stretching begins, pressure is cut od from thepiston-cylinder assemblies 39C1 through 39C5 and the valves 39V1, 39V2,39V3 and 39V4, for example, opened to exhaust. Fluid in the two smallpiston-cylinder assemblies 23 is maintained under suicient pressureduring a stretching operation so that the resistance otered therebytogether with the friction between the platform 21 and the base 22prevents the entablature and the elements attached thereto frominadvertently sliding along the base 22. Due to the slight change inlength of the bars 13 caused by the compression loads imposed thereon,the frames 42 will move a. slight distance along their bases 44.

However, should the workpiece be ruptured during a stretching operation,a tremendous amount of energy will suddenly be released thereby imposingupon the structure exceptionally large forces which must be properlyabsorbed in order to prevent damage to the apparatus. As mentionedabove, during a stretching operation, the bars 13 areV placed undercompression and actually becorne elastically shortened. When a workpiecebreaks, the push rods 36 and 36a, being limber, are caused to buckleelastically by the longitudinal shock forces imposed thereon so that thejaws are pulled open immediately, thereby releasing the ends of thebroken plate held therebetween and avoiding damage to the jaws. Then,too, the piston cylinder assemblies 39C1, 39C2, 39C3, 39C.,L and 39C5,having been previously exhausted, offer very little, if any, resistanceto outward movement of the rods 36 and 36a. Furthermore, when breakageoccurs, the hydraulic pressure within the piston-cylinder assembly 15 isreduced rapidly and the crosshead 17 moves immediately outward to theleft, the movement being resisted, however, by the action of the pullback v piston-cylinder assemblies 26. Of utmost importance, also, is thebehavior of the two bars 13 at the time a workpiece breaks. Immediatelyon relief of the compression load upon the bars 13, the bars are causedto extend Very rapidly, i.e. more rapidly than the hydraulic pressuredecreases in the-main cylinder, the net result of which is to cause theentablature 19 together with the platform 21 connected thereto to tendto be moved to the right. This tendency is resisted by the frictionalforces oEered by the platform 21 and base 22 at their points of supportand by the hydraulic pressure of the pull back cylinders 26 and thepiston-cylinder assemblies 23. The total released energy when a platebreaks is absorbed by the permitted motion of the assembly against theresistive forces-the forces being reduced in proportion as the permittedmotion is increased. When, on breakage of the workpiece, displacement ofthe platform 21 to the right takes place, the piston-cylinder assembliesof both the preferred form as well as of the 7 icidfiedvpfrm ofinvention are ofsuticient capacity to rfefv "tlieappa'ratusto Vitsoriginal Positionen Then, too, th 'capacity' ofy the pull backpiston-cylinder assemblies 26 1s' siuflicientlygreat to return thecrosshead 17 and the movable head 12 connected thereto to their originalpositions to the right, Figure V1,'after displacement to the left hasoccurred on breakage of a workpiece. Of course, under many conditions ofoperation, the frictional resistance to movement between the entablatureand the platform will, at times, be of sufficient magnitude to preventany movement of the entablature relative to the base, whereas theresistance to movement offered by the frictional resistance as well aseither the piston cylinder assemblies` 23 or 66 will be overcomeprimarily under those conditions of operation where the shock lenergyof,V such intensity that damage to the foundation and possibly-to otherparts of the apparatus would result if the entablature were trmlyaixedto the foundation.

lIn accordance with the provision kof the patent statutes, 'We haveexplained the principle and operation of our invention and haveillustrated and described what we consider to represent the bestembodiment thereof. However, we desire to have it understood4 thatwithin the scope of the appended claims, the invention may be practicedotherwise'than as specically illustrated and described.

l We claim:

l. Apparatus for performing a stretching operation upon elongatedworkpieces comprising a normally stationary workpiece gripper head, amovable workpiece gripper head, av pair of carriages interposed betweensaid heads` adapted toy support a workpiece thereon, transverselymovableside'guards mounted upon said carriages en'gageab'le with and forcentering a workpieceton said carriages, means foradjusting saidstationary head inra direction toward and 'away from said movable head,a pair of longitudinally extending parallel bars having spacedtransversely opposite openings in the sides thereof, pins carried bysaid stationary head adapted to be inserted in said openings'therebyl tosecure said normally stationaryV head ina selected position along saidbars, an lentablature Vrigidly secured to saidbars, a cross head,afpairof'links connected to said movable head and to saidcross head,power means operatively connected to said 'cross headv and to saidvventablature, adaptedtol die; place said cross` head in a direction awayfrom said enfL tablature and said normally stationary head, guides, e,

cured to said ent'ablature and in slidable engagement with 'said links,a baseupon which said entablatupe is slidabl'ymounted, yieldable meansin` engagement: @19 normally restrainingimovement of' saidentablatureS/upon said base during a stretching operation andoperatively arranged Yto permit relative movement betweenjsaid`entablature and said base in the event breakage of awor-kfY piece occursduring a stretching operation thereby to prevent damage to saidapparatusfrom sudden shock forces incident to such breakage and toreturn said entablature to its original position after suchrelativernpvement takes place.

2. Apparatus for performing a stretching operation upon elongatedworkpieces according to claim 1 in which said.-gripper heads include aplurality of pairsv of workpiece gripper jaws positioned transverseiyacross said apparatus, push rods operably connected to each pair of saidjaws and means operably secured toyand for simultaneously actuatingsaid. rods thereby to close said jaws simultaneously in grippingrelationship with the work` piece, said rods being adapted to buckleelasticallywhen forces are imposed thereon by the sudden release ofenergy in the event of breakage Ofva workpiece during a 'stretchingoperationithus to withdraw said jaws andto release the portions of aworkpiece engaged therebetween.

References Cited in the ileof this patent

